The world we are currently living in is, in dimensional terms, called a three-dimensional world or a quasi-four-dimensional world. Pen % fun % Pavilion www.biquge.info

In terms of the most basic mathematical concepts, the three-dimensional world is easy to understand. Here's how it goes:

The primary metaverse refers to the extension from one point to one direction. In layman's terms, it's a ray.

The two-dimensional world refers to starting from a point and extending horizontally and vertically. In layman's terms, it is a plane.

The three-dimensional world refers to starting from a point and extending horizontally, vertically, and vertically at the same time. Generally speaking, it is a three-dimensional structure that develops in length, width and height at the same time.

The world we are currently in is a three-dimensional world, because all the spaces we live in and produce are positioned through three factors: length, width and height. Of course, the point that is the origin is only a reference and can be changed at any time, but the relative length, width, and height are unchanged.

Why do we come up with the concept of a quasi-four-dimensional world that is smaller than three and smaller than four? There are three levels of understanding.

The first rudimentary understanding is determined by strict Newton's laws. Let's give a simple example of a complex truth:

For example, let's make a chest, and let's say the box we want to make is a standard box. Then the wood used and the size of the space created by the design are determined by the length, width and height of the box. This is a typical three-dimensional world. We only need to determine the length, width and height to make the space we need, and we can also confirm the cost of the materials we need to pay.

Based on this, we will generalize, for example, we want to build asphalt roads. To build an asphalt road, we need to lay a section of asphalt on the roadbed, how much asphalt is needed? Confirm the three factors of length, width, and height, and we can confirm how much asphalt we need. In fact, if you cut the asphalt road crosswise, you will find that we are actually building a rectangular body made of asphalt. The size of this cuboid determines how much asphalt we put into it.

Building an asphalt cuboid seems to be no different from building a wooden box.

But if we build on that and then generalize, we will find that the concept needs to be extended.

When we build asphalt roads, there are technicians who measure the flatness of the road surface through precision instruments, for example, if the error within 100 meters does not exceed 0.05 meters, it may be qualified. That is to say, within 100 meters, if the error of the height and fluctuation of this plane does not exceed 0.05 meters, it can be regarded as a plane. Then, the total amount of asphalt required can be thought of as the width of the pavement multiplied by the depth of the asphalt and then multiplied by the length of the pavement. In fact, it is the cross-section of the asphalt road multiplied by the length of the asphalt road.

Well, we can control the error within 0.05 meters of 100 meters of asphalt road, 10,000 meters, 10,000 meters, or even 40,000 meters, and we can control this error standard - as long as we are willing to pay this cost and effort.

Stretch a little further.

Suppose we build a 40,000-kilometer asphalt road along the equator from any point along the earth's equator, and the requirement is that the error is controlled within 0.05 meters. As long as we are willing to pay the cost and effort, we can theoretically do this.

In order to achieve the standard of error control, every 100 meters of technicians must order a shutdown and use the instrument to measure and correct in time. From the technician's point of view, he only needs to ensure the error within every 100 meters.

We don't think about the roadbed, we only think about the problem from the perspective of a technician.

Then, it is easy to confirm that as long as the technicians strictly implement the standards, when repairing to 40,000 kilometers, the undulation error of this asphalt road has been kept within 0.05 meters.

That is, in the eyes of technicians, this asphalt road has always been a plane with a fixed width and depth and continuous extension.

If you were a technician at the time, you would definitely be like this. But now that you're a magistrate, do you think so?

Probably not.

Because we all know that the earth is round, with a circumference of about 40,000 kilometers, and if you follow the equator for 40,000 kilometers, you will return to the original point.

-- We walked back to the starting point from behind us.

-- To put it simply, we think we are moving on a plane, but we are actually moving on a circular surface.

Well, the core content of this is that we are a three-dimensional world, and even if we think that we are moving in a flat two-dimensional world, in fact, we are also moving in a three-dimensional world on a curved surface.

There is also a more important law implicit here: when the quantity changes to a certain limit, the qualitative change occurs.

For example, within the limits of 100 meters, 10000 meters, and 10,000 meters, it can be considered as an absolute plane from the perspective of the surface.

-- Because compared to the overall length of 40,000 kilometers, 100 meters, 1,000 meters, and 10,000 meters are insignificant, and they do not have an advantage in numbers. But if the quantity accumulates to a certain amount, such as less than 40,000 kilometers, only 20,000 kilometers, you will find that the plane that you have always thought has already changed to a surface.

In the process of quantitative change to qualitative change, the ranking officials must pay attention to it, because this is an important theoretical basis in the future.

The second intermediate understanding has the embarrassment about Newton's theory.

Back to the classical theory.

Newton's theory of managerial mechanics, generalized in the universe so large, is still valid.

-- This is not only what he thought in the old man, but also in the general public.

This is not to blame for his old people and the general public. Because through Newton's classical mechanics, we have at least defined the trajectories of the major planets in the solar system. We calculated the trajectories of the eight planets and confirmed them in our observations. We also calculated that there should be a relatively large object beyond the eight planets, and later observed that we once named it the ninth planet, which is Pluto. Of course, because Pluto was not massive enough, it was later eliminated from the series of planets. However, it is precisely because most of them are not calculated enough, which shows the wisdom of Newton's theory.

You can see how powerful Newton's theory is! By smashing an apple on the door of his head, he can invent a theory that covers the solar system.

It's a pity that Apple is too small after all.

Before 1900, Newton's theory was the supreme classic, and all worlds, except for superstition and imagination, our real world was one world - all Newton's three-dimensional world.

After 1900, the world changed because of one man - Albert Einstein.

Please note that this is also a process of quantitative change to qualitative change.

The accumulation of accumulation, mainly concentrated in one point, is the trajectory of Mercury.

The ancestors of the Chinese have a famous saying that is particularly classic, called: The king begins with this, and must end with this.

-- What you are best at, what you die in the end.

To put it mildly, you're the best at whisker shooting, and you're going to die on whisker shooting: either you're shooting wrong, or someone else is better than you.

To put it mildly, you are the most respectable because of tolerance, then you will inevitably die of tolerance, because the tolerant partner has always been indistinguishable from wrong; you are famous because you are smart, and you must fail because of your cleverness, because the smart partner has always been cunning, and if you are not careful, there will be a moral problem, or you will be clever and mistaken.

Newtonian classical mechanics was famous for calculating huge and distant celestial bodies, and it was also embarrassed by celestial bodies.

-- The trajectory of Mercury has always been inexplicable by Newtonian mechanics. Mercury, a kid, doesn't play cards according to common sense.

Many scientists in history have noticed this problem, but they couldn't solve it at the time. But it is because of this dedication that human beings are touched: although they could not solve it at the time, they recorded the data they observed, accumulated it, and left it to future generations to solve.

Later generations really pushed this accumulated quantitative change to a qualitative change and solved it, and this descendant is Einstein.

Einstein pointed out the shortcomings of Newtonian mechanics: light is not straight, it bends under the action of gravity. This is the core of general relativity.

Don't stick to the description of general relativity in the textbook, you will find that you can't understand what is described in the textbook.

You are not to blame for this, because when the general theory of relativity was born, except for one person who could understand it, because he really did, no one else could understand it except Einstein himself. Even now, it's not much better.

Newton's classical theory states that light is straight, and general relativity denies it. Excluding the abstract formulas and dogmas of general relativity, we say that the core of general relativity is that light is not straight, it bends under the influence of gravity.

That's amazing.

Because under the traditional Newtonian classical theory, light is straight. Even on such a long plane as the earth, the straight line will be curved, but the light will still be straight when it hits the earth, otherwise there will be no difference between spring, summer, autumn and winter.

In fact, as early as 1915, we proved Einstein right. That is, light bends under the force of gravity.

Then, the three-dimensional world is not just a qualitative change caused by a quantitative change of a long enough plane.

The three-dimensional world becomes unstable, and it needs to introduce other dimensions to fully describe things.

The light we just talked about is a factor. But light cannot be defined as a dimension, but it can be defined in terms of speed. So the speed of light is a common dimension other than the third dimension, which we call the fifth dimension.

The third advanced understanding is to revert back to the special theory of relativity.

Some careful officials will ask: After the third dimension, go directly to the fifth dimension, but what about the fourth?

Makes sense, because the fourth dimension is time. This is still related to general relativity.

General relativity didn't pop out of a rock, it was preceded by special relativity.

The core of the special theory of relativity is also called in layman's terms: two identical tables will travel more slowly on the table moving at the speed of light than on the table at rest.

Someone will have a lot of things: whether the start time is consistent, whether the quality of the table is consistent, and so on.

As I said, two watches are exactly the same, all the factors are the same, but one starts to move at the speed of light, the other is stationary, and after a period of time, we will find that the time of the two watches is different, one is fast and the other is slow. Of course, the difference is small, but there is definitely a difference.

It can be seen that the most important factor of special relativity is time.

Therefore, time is the fourth dimension after the third dimension of our classic. The fifth dimension is the speed of light.

Our current real world uses time, time is everywhere, so why not call it a four-dimensional world, but a quasi-four-dimensional world, or even a three-dimensional world?

The reason for this is that we don't really have real control over all the properties of time.

We only know a little scratch of the surface.

Let's take a vulgar example.

Let's say you're a boy with a girl you've always loved and married someone else. From the moment she gets married, you will never have a chance to be her first groom. Because even if you kill the groom and marry her, she is still a second marriage, not a first marriage, which means that you are not the first man to marry her. In the classic three-dimensional or quasi-four-dimensional world of reality, you can't do it.

But if you can go back in time to before she got married, you have a chance to be her first groom. There is no other way.

But now we just know that if we can go back in time, we have a chance to change the world, but we don't know how to go back in time.

Therefore, we have not really realized the four-dimensional world, and at best we can only call it a quasi-four-dimensional world.

To promote it again, we call the current classic dimensions other than the three dimensions, because they are different from the usual three dimensions, so they are called different dimensions, and those worlds are collectively called the worlds of different dimensions.

Each dimension is also called a dimension, and the world above three dimensions is also called a high-dimensional world.

The story we are going to tell now takes place in another dimension. To be exact, it takes place in the fourth extradimensional world a few further after our present world.

Note that it is not a four-dimensional world, but the fourth other-dimensional world in chronological order.

The world is very much the same as us, but it is very different.